Sanding drum



NOV. 8, 1932. I R PONSELLE 1,886,733

SANDING DRUM Filed Dec. 29. 1927 MM(ZW ATTORNEYS Patented Nov. 8, 1932 curren era-res ROBERT A. PONSELLE, NEW YORK, N. Y.

SANDING DRUM Application filed December 29, 1927. Serial No. 243,235.

This invention relates to drums for abrading, polishing, and similar purposes, of the type used in various machines, such as those employed in working wood or polishing 5 metal, leather, and'the like, these drums being power driven and having a working surface which is brought into contact with the article to be operated on. The present druln is one capable of use in machines of numerous rg kinds, and while constructed primarily for use in portable machines for surfacing hard wood floors, its utility, as will be apparent from what follows, is by no means limited to that particular application. In drums for working floors as now constructed, the workingsurface is provided by means of a sheet of abrasive cloth or paper wrapped around the surface of the drum. As this sheet performs the abrading action, it ail-must be held tightly in position, and lie flat on the drum surface so as to be supported thereby, since otherwise it would slip, wear unevenly andbecome torn. The securing of the sheet to the drum is a problem of considerzfi-able difficulty and numerous attempts have been made to solve it; For example, the drum has been provided with a slot in its periphery into which the ends of the paper are passed, and slotted shafts are mounted within the ac drum near the slot so that the ends of the paper may be passed through their slots. With the paper in this position, the shafts are turned to draw the paper taut. This construction is far from satisfactory as the sheet is not uniformly tensioned, and replacement is a difficult operation asthe' parts are inaccessible. The object of the present invention is to provide a drum of the type described, whichv 4c is provided with means by which the working sheet may be held securely in position fiat on the drum and under even tension, the improved holding means being of simple con-' struction and permitting ready replacement of the sheet. In the new drum the ends of the working sheet are held securely, and when the drum is'at rest the securing means may' be rendered'readily accessible,-but when the drum is 111 operation it presents a substan- -t1ally continuous cyl ndrical surface over which the sheet lies smoothly and under'uniform tension.

In the new drum the drum structure preferably includesa main drum member consisting of a cylindrical surface and end plates. A portion of the cylindrical surface is cut away and replaced by a plate'preferably of segmental form which is movably mounted in the drum structure and" provided with a grip-ping device at one end; This plate is movable to different positions, in one of which it closes the opening in the cylindrical surface, while in another position it lies at some distance from'this opening. The drum'memher is provided with a gripping deviceiadjacent to or at one side of the opening and in these gripping devices may be held the ends of the working sheet which extends around the drumand over the plate. When the plate is in open position, the distance between the gripping devices around the drum is less than this distance when the plate is disposed so as to close the opening. In order to secure the iwork sheet in position, the plate is moved away from'the opening and the ends of the work sheet are inserted in the gripping devices and secured to it. The plate is now moved to closev the opening and complete the drum, and in such'movement the plate has a lever action which exerts tension'on the sheet. Preferably the plate is pivotally mounted at a point within the periphery of the drum, and in open position the end of the plate carrying the gripping device projects outwardly beyondthe drum surface, so that both gripping devices are exposed. The plate may then be swung to close the opening in any suitable way and at the same time put tension on the sheet,'but preferably the plate is suitably balanced on its pivot so that when the drumis rotated, centrifugal force acts on the plate, moving it to closing position and holding 1t in that position throughout the rotation of the drum. By i such movement of the plate, the sheet is ten- ;sioned and this tension is maintained by the centrifugal force. Also, it is preferable to provide the segmental plate with alight spring so that when the drum stops,tl1e segment is caused to swing on its pivot away ioo means so that although they "are ordinarily held in gripping position with considerable force, they may be opened for withdrawal or replacement of the abrasive material without diiiiculty. The drum is also provided.

with a layer of cushioning material on its outer surface and adjacent the opening in the drum surface through which, theends of the abrasive material pass, novel supporting means forthe cushioning material are provided which prevent the tension placed on the abrasive material from flattening the cushioning layer to an extent such as to make the drum surface irregular. The new drum also includes convenient means for counterbalancing the weight of the segment and its associated parts and an exact counterbalancing may be accomplished without dismantling the drum.

For a better understanding of the invention, reference will be made to the accompanying drawing, in'which Fig. 1 is a view of the drum in side elevation, certain of the parts within the drum being indicated by dotted lines,

Fig. 2 is a sectional view on the line 2-2 of Fig. 1,

Fig. 3 is an end view taken as indicated by the arrow in Flg. 1,

Fig. l is an enlarged sectional view showing' means for preventing the flattening of the cushioning layer by the taut abrasive material, and

Fig. 5 is a similar View showing a modified form of construction.

The new drum assembly includes the drum proper, a layer of cushioning material, and

awork sheet. This work sheet may be of any suitable material, such as sand or'garnet paper or cloth, leather, etc. i For convenience, the work sheet will be referred to as paper, though it is to be understood that any suitable sheet material maybe used for the purpose. j

The drum comprises a substantially cylindrical member provided with end plates 11 and preferably the cylindrical member and end plates aremade in one piece by a suitable casting operation. The cylindrical member 11 is cut away to form an opening extending from one end plate to the other, and this opening under proper conditions may be closed by a segment member 12 which consists of a casting having a curved surface 13 and end plates 14: by which the member 12 is pivotally mounted on a shaft 15, the ends of which are-received in bosses 16 in the drum end plates 11. Attached to the segment member and to the inner wall of the casing is a spring 17 of light construction and so arranged that when the drum is at rest, the spring rocks the segment on its pivot to the position illustrated in Fig. 3, in which the end 18 of the segment projects outwardly beyond the cylindrical surface of the drum, 7 while the end 19 lies within the drum surface. when the drum is in rotation, the segment member occupies the position shown in Fig. 2, due to the fact that the member is off-balance on its pivot and centrifugal force acting on the member will cause it to swing to the position illustrated. At its rear end, the segment member is provided with a shoulder 20 which abuts the inner face of the peripheral surface of the druinadjacent the opening in which the segm'ent is disposed, when the segment is in its outward position 2) and in that position the curved surface of the segment forms substantially a continuation of the outer surface of the drum, the end 18 of the segment lying close to the edge 21 of thecylindrical lng.

At vided with an inclined plate 22 formed as a continuation ofthe curved surface 13 and in the end members 1a of the segment member is mounted a shaft 23 onwhich is pivotally surface of the drum at the openits end 18, the segment member is promounted the clamping aw 2%. One end 25 of this jaw adapted to bear against the inclined plate 22 for gripping purposes, and the'other end of the jaw is provided with a tail. 26

which lies against a stud shaft 27 mounted in one end member of the segment member. A spring 28 encircling tne shaft 23 s arranged to cause the aw member to swing on its pivot to force the tail toward the shaft 2? and this shaft has a flat portion such that when the flat portion is presented to the tail, the spring 28 may swing the jaw member so that its gripping end 25 is forced tightly against the plate 22. The shaft 27 is provided with a boss 29 at on'elend, in which is a slot-like recess 30, and the end plate 11 adjacent the boss 29 is provided with an opening 31. By swinging the segment member on its pivot,

the boss will be exuosed throu h they ooenin a 1 a; j. a:

31 and a tool may be inserted in the recess 30 and the shaft rotated so that its curved portion bears against the tail 26 of the jaw and swings the'jaw to move its'end 25 awayfrom the inclined plate22., The jaw may thus be opened conveniently from the outside of the drum. Vv hen the tool is inserted through pening 31 into recess 30, the tool holds the plate 12 against the action or o spring 1?. i Formed asa continuation of the outer drum wall adjacent the ecge 21 is an inclined plate 32 and mounted on a shaft 33 extending from one'end of thedrumto the other is'a clamp ing aw 34 having a gripping portion 35 cooperating with plate 32, and a tail 3G. The

n ane shaft 33 carries a spring-28f normally fore.-

in the-j aw into gripping relation with; respect to plate 32, in which position the tail 36vlies close to a stud shaft37 mounted ina suitable .boss in the'end plate of the drum and carry- 1 ing a bushing 38 atitsexposed end-, provided with a slot-like recess 39. The shaft-37 has a fiat portion which is turned towardthe tail 36 when the jaw is to perform its grippirgg action, but when the shaft 37 is turne means of its bushing so that a curved portion of the shaft bears against the tail 36 then the jaw is swung tolopen position.

The outer surface of the drum is covered by a layer of cushioning material e0 which may be a sheet of sponge rubber or; other suitable material for the purpose. This cushioning sheet is secured to the drum face at suitable points and extends over the segment, being secured to the end thereof-which lies outside of the drum surface. when. the drum is atrest. The length of the cushioning layer is such that when the drum is in rotation, as illustrated in Fig. 2, the ends of the cushioning layer will lie close together and be separated only by the thicknesses of paper which pass between them and are gripped by the jaws.

In attaching" the abrasive paper to the: .1 drum, the shaft 33 is turned so as to open the jaw 35 and one end of the abrasive paper, is slipped between the jaw and the plate" 32. When this end is in proper position,1the shaft, turned so as to release the-j aw and the latter grips the end or" the paper under the influence of its spring 28. The free endof the paper is then weund around the drum and over the segment and the latter is swung manually on its pivot to bring the boss 29 opposite the opening 30. A tool is now inscrted through the opening and the stud? shaft 27 is rotated to the extent necessary to swing the clampingja-w to open position.

The end of the paper is then placed between the j and its bearing plate and the stud shaft rotated to present its flat surface to the tail of the jaw, whereupon the j awewill grip,

the end of the paper tightly under the action, of its spring. lVhen the parts are released,

the spring 17 will restore the se ment to.tl1efioth ends ofv the paper are new grippedin'the clamping jaws, but the paper is not drawn taut against,

position illustrated in Fi the cushioning surface. When. the drum is rotated, however, centrifugal action, swings thesegment on its pivot tothe positionillustrated in Fig.2, in which-position the curved portion of the segment memberforms a continuation of the main cylindrical part of the drum, and tension is placed onthepaper.

which draws it taut and holds it in-that posi- I tion, throughout rotation. As the paper is drawn taut, rt has a tendency to flatten} the edges of the cuslnomngmember atthe points Y 41 and42 which are adjacent the pointwhene theends'of the paper'pass into the drum tothe j aws. To-prevent such-flattening action,

Iprotzide the end of the segment and the end of the drum at the point where the ends of the paper pass to the jaws with plates 43.

and M which are secured to the respective parts in; any convenient manner, as'bysmall screws45. These platestS and Mare of thin sheet metal and project outwardly beyond the; drum and segment wall for a distance; somewhat less than the thickness of the. cushioning layer- Whenthe layer is compressed by thetension 01" the paper, the plates hold. thelayer in position and prevent compression to anextent which would cause the drum to; havea flat surface at the opening around the ends ofthe cushioning member and'overlie the ends of the segment and cylina "drical surface of the drum, as indicated at 49. WVh-en the ends of the paper are drawn taut and the cushioning layer is collapsed, the sheet metal members 46 areforceddown- Wardly toward the drum surface to a; slight extent, but the portions of the plates'which' overlie the ends of the cushioningmember prevent its being flattened by the tension of the paper toan extent suificient toj form aflat place. onthe drum.

shaft 28' lies substantially in the plane of the gripping face of the inclined'plate 22 and the It willbe noted, Fig. 2, that the axis of. the

bearings for this shaft similarly lie in the plane of the face 'ofthe plate. likewise the shaft 33 with its bearings lies, substantially inthe plane of the operating face of the inclined plate32. With this arrangement, the

bearings serve as stops for the endsof'the sheet of sandpaperorthe like which is used to cover the drum.

In, drums of this t e used for surfacine floors, for example, it is very important that the papershould be under substantial tension which should not vary beyond certain limits. Accordingly, the paper used with a drum of any given size is cut to an: exactlength. ap-

propriate'for that drum and when the paper is mounted. on the; drum the endsshould be inserted in' the j aws in suchm anner that thereis one jaw to the other around the drum' If the workmanis:carelessand inserts the paper a definite length of. paper in the space from in the jaws in such manner that the distance along the paper between the jaws is greater than it should be, the segment, when swung an operation of the drum, will not draw the ,paper right and as soon as the rotatingdrum comes in contact with the surface to be opment as soon as the latter is swung by the action of the centrifugal force is likely to be sufiiciently great to rupture the paper and thus require the insertion of a new piece.

lVith the present construction, these difficulties are readily avoided. In inserting the paper in position, the segment is swung outward in the direction suggested in Fig. 3 until both jaws are exposed. The workman inserts one end of the paper between the jaw and the plate on the segment and in doing so, moves the paper until its end abuts the shaft bearings which thus serve as a stop. The paper is then wrapped around the drum and its other end bent around the edge of the opening in the drum surface and its end inserted between the jaw 35 and plate 32. Here again,

the end of the paper is moved along the inclined plate until it strikes the bearings for shaft 33 which serve as the second stop.

provided, it will be apparent that theworkman can mount the paper in proper position without difficulty and in such manner that there is an' exact-length of the paper lying between the aws in the direction around the drum and this length of paper is justsuificient so that it will be properly tension'ed and wrapped tight aboutthe drum surface when It will be noted that of the segment around which the paperiswrapped are both relatively wide and the plates 22 and 32 are inclined at such an angle that the paper is bent through an angle of less than 180 at its ends when being placed in position. The paper used inthese drums is relatively stiff and it can not easily be bent through a sharp angle. With the present .construction the a er is bent throu h an easy curve and by the provision of the stops,

the workman has no difliculty in mounting the paper in position. It will be apparent that the placing of the shafts with their bear- ,..:ings in the position illustrated provides asimple stop which servesthe desired purpose of assisting the workman in mounting the paper in position,-although stops of other construction might similarly be used.

2.1.213 lVhen the plate is swung onitsaxis to a.

position in which its projecting outer end is in outermost position, the inclined gripping surface of plate 22 lies at one side of aradius through the center of the cylinder and the outer edge of surface 22. The surface lies at the same side of this radius as the other plate 32 mounted in the body of the drum. When the gripping surface on the plate 12 fulfills this condition, it is a simple matter to bend the end of the stiff abrasive sheet around the end of the cushion layer and around the edge of the plate 12 into position to be gripped by jaw 25. Should the inclined surface 22 lie at the other side of the radius referred to, the extreme end of the sheet would have to be bent through a greater are and because of the character of the sheet, its end could be inserted in the gripping jaw on the plate 12 only with the utmost difficulty.

The drum is mounted for rotation in any convenient manner on the shaft, as for example, the end plates may be provided with bosses 50 through which the shafts extend, the drum being secured to the shaft in any desired way. Since the segment, the jaws and their associated parts are at one side of the center of the drum, provision must be made to balance the drum and for this purpose a solid weight 51 is cast within the drum opposite the segment and extending from one end of the drum to the other. As this weight 51 will not ordinarily give an accurate counterbalance, the end plates of the drum are provided with open channels 52 in which suitable additional weights may be placed from theoutside of the drum. tion'of the weights, the drum may be evenly balanced so that it will run without pounding.

It will be seen that in the new drum the paper may be placed in position on the surface of the drum and its ends secured in the gripping devices without the necessity of putting that tension on the paper which would be required to hold it rigidly in position during'the operation of the machine. With drums as heretofore constructed, the paper is wrapped about the drum ,and attached thereto and its ends are then drawn up so as to make the paper taut. This is a diflicult operation and results in non-uniform tension which gives the paper a short life. With the present construction the drum is so constructed that its periphery may be considerably reduced in length by swinging the plate'sothat the mounting of the paper in position and the securing of its ends is a simple operation, and it is not necessary that the paper should have its ultimate tension while its 'ends are thus being secured. simply laid smoothly in position on the surface of the drum and its ends gripped. Thereafter the segmental plate may be restored to complete the cylindrical surface of After mental plate the tension is applied.

It is.

the 'paper isput position'the plate may be "restored to normal operating posltion in any I prefer, however, to construct the plate in the manner heretofore disclosed, so that centrifugal action will apply the force necessary to restore the plate to close the opening in the drum. I have found that in a drum thus constructed, a segment of relatively light weight may be so balanced that at normal opcrating speed a tension-of over onehundred pounds may be placed on the paper. This tension is exerted gradually as the drum approaches perating speed, and during the gradual application of the pressure the paper is under uniform tension so that the stress is evenly distributed.

With the present drum it that all of the operat g parts ar normally concealed but are readily accessible when occasion arises. It is not necessary, therefore, to remove the end plates of the drum, or otherwise take it apart if it should be desired to get at the interior of the drum. The operating parts of the new drum are all of simple construction and may readily be ma,- nipulated so that replacement of the paper is a simple operation whi h does not require any considera le amount of time. While the drum has been illustrated as consisting of a main body portion and end plates of integral construction, it will be apparent that the end plates may be made separate from the body, and numerous other changes be made without departing from the invention as set forth in the following claims.

I claim:

1. In a drum, a body having end walls and a cylindrical wall provided with an opening extending lengthwise of the drum axis and substantially from end to end of the drum, a plate of segmental form mounted within the drum on an axis lying between radial planes passing through the edges of said opening,

will observed and balanced to be swung by centrifugal forceto close the opening, a gripping aw carried by the body and cooperating with a portion thereof adjacent one side of the opening, a gripping jaw carried by the plate and cooperating with a portion thereof, the gripping jaw carried by the plate lying adjacent the first gripping jaw when the plate is in closing position, a pair of stops, one associated with each gripping and a surface sheet extending around the drum and over the plate, this sheet having one end held by the j aw on the plate and the other end held by the jaw on the drum, one end of the sheet passing around the edge of the body at the side of the opening, and the other end of the sheet passing around one end of the plate.

2. In a drum, a body having end walls and a cylindrical wall provided with an opening,

a segmental plate pivotally mounted within the drum out of'contact with said end walls,

means within the drum operable when the "drum is at rest' for' holding the plate with one end projecting beyond the surface of the drum, said plate being balanced to be swung by centrifugal force upon rotation of said drum toclose said opening,a gripping device carried at the saidend of the plate, a grip-.

ping device disposed within the .drum at one side of the opening and adjacent theprojecting end of the plate, a surface sheet extending around the drum and over the plate and having its ends held by the said gripping devices, and means operable from the outside of the drum for controlling the operation of the gripping devices. I

8. In a drum, a body having a cylindrical wall, a portion of which is cut away to form an opening, a plate having a. segmental surface pivotally mounted within the drum adj acent the opening, this plate being balanced to be swung by centrifugal force during rotation of the drumto a position in which it closes, the said opening, a spring-pressed gripping aw carried the plate and cooperating with a portion thereof, a spring-pressed gripping jaw carried within the bodyand coo cratin witha ortion thereof and means P a P. 7

for moving the gripping jaws to open'position. s N

I 4.111 a drum, acylindrical body a portion of which is cut away to form an opening extending lengthwise of the surface of the drum,

plates closing the ends of the body, a plate having a segmental surface pivotally mounted in theend plates and adapted to be swung to close the opening in the body, means engaging the plate and operable for holding it in open position when the drum is at rest, the plate being so balanced as to be swung to closed position by centrifugal force in the rotation of the drum, and means carried by the drum and by the plate for gripping a surface sheet to be laidabout the drum and over the plate.

5. In a drum the combination of a cylindrica'lbody provided with end plate, the body havingan opening in the wall thereof, a plate pivotally. mounted within the body and adapted-to be swung to close the opening, a grippine jaw carried by'theplate and coopcrating with a portion thereof adjacent one side of the opening, a gripping aw carried by the drum and cooperating with a portion thereof :at the saidside of the opening, springs forcing the gripping am; to operative position, and a shaft for each jaw adapted upon rotation to swing the jaw toopen position, these shafts being operable from the outside of the drum. V v i 6. In a d-rum, .a body having a cylindrical wall, a portion of'which is cut away to provide an opening, a plate mounted within the body and adapted to be moved to close the opening,

55 .7 the cylindrical wall of the body without sub- 60 body at one side of the opening therein, and

an extension from the plateat one end thereof turned toward the interior of the drum, a gripping aw mounted in the plate and spring pressed against the extension, this platehavinga tail, a shaft in the plate adjacent the tail, this shaft being operable upon rotationto bear against the tail andswing the jaw away from the extension, and gripping means carried by the body at one side of the opening and adjacent the gripping means carried by the plate.

7. In a drum, a cylindrical Wall having an opening, a plate pivotally mounted within the drum and adapted to be swung to close the opening and complete the drum, means carried by the plate and by the drum adjacent one side of the opening for holding the ends therein, the body being provided with a gripping surface lying inside the periphery of the body and extending inward from the outer surface of the body at one side of the opening and at an acute angle to a radial plane passing through the edge of the opening and the axis of the drum, a gripping jaw arranged to cooperate with said surface and accessible through the opening, a plate mounted within the drum and movable to close the opening, this plate having a gripping surface formed as an inward extension from the surface of the plate, said gripping surface lying adj acent the first gripping surface when the plate is in closing position, and the surface on the plate lying at an acute angle to a radial plane and adapted to cooperate with the gripping surface thereon.

9. In a drum, a body having a cylindrical wall provided with an opening, a plate I mounted in the body on an axis lying between radial planes passing through the edges of said opening, said plate being balanced to be swung by centrifugal force during rotation of the drum to close the opening and complete stantial gaps, a gripping surface 011 said plate at one edge thereof and inclined to the surface of the plate, a gripping jaw cooperating with said plate, a gripping surface on the a gripping jaw cooperating with said gripplng surface on the body, the gripping surface on the body, when the plate is in its extreme open position, lying at the same side of 1,see,7se

a radial plane through the axis of the body and the outer edge of said surface as the second gripping surface.

In testimony whereof I affix my signature.

ROBERT A. PONSELLE. 

